It's one of the most popular party drugs in circulation at the moment, but what is it? Is it a new danger or old news? There's a lot of misinformation out there, so we talked to an expert to find out what you need to know -- especially as the summer music festival season remains in full swing, and students prep to head back to campus.

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Molly is a slang term for MDMA, an illegal drug that is classified as both hallucinogen and a stimulant. It's generally accepted that the name Molly is derived from "molecule."

MDMA is a synthetic drug with the full title "3,4-methylenedioxy-methamphetamine," but it's also commonly referred to as ecstasy. However, Molly may be a little different than ecstasy -- it depends on whom you ask.

Confusion about the drug's purity is what makes MDMA especially dangerous, said Dr. Joni Rutter, the director of Basic Neuroscience and Behavioral Research at The National Institute on Drug Abuse (NIDA).

"Even in its purest form, it can cause fatalities," she said. "It's still a drug and we don't know a lot about its effects."

The assumption that Molly is purer is controversial. Both drugs can be mixed with ("cut with") other substances, which can be extremely dangerous. Ecstasy can be harder to tamper with once it is in pill form -- but as a powder, Molly can be mixed with many other substances.

Some experts suggest that due to Molly's popularity, it is now also just as likely to be cut with other substances as ecstasy.

3. What does Molly do?

MDMA is a popular drug at parties because of the euphoric effects it has on the user. It has become an increasingly common concern for concert promoters, campus police and local officials in the last few years.

Dr. Rutter said that party-goers favor MDMA because it will make them feel "energetic and euphoric."

"It wreaks a bit of havoc on the brain," she said.

The effects can be different for different people, but MDMA works by increasing the activity of three neurotransmitters in the brain.

"Users have overall good feelings towards others," Rutter said. "The hormones that are released make people feel more social."

But with the good feelings come some nasty side effects. Rutter said users often report feeling anxious and confused. She also said that some people lose their grip on the passage of time. More information on the effects of MDMA is available from NIDA's website.

MDMA has been linked to a spate of recent deaths that may have been caused by the drug.

Two people, ages 17 and 20, recently died in Maryland, after being taken from the Mad Decent Block Party at Merriweather Post Pavilion in early August. Police said they thought both victims had used MDMA, but were awaiting toxicology tests. Twenty other people were also taken to hospital for apparent drug-related problems from the music festival.

NIDA's Dr. Rutter said that the biggest risk to users will be hyperthermia, or extreme overheating, probably caused by blood vessels failing to dilate enough.

Rutter said that this was especially an issue in a club or festival environment, where users are exposed to high temperatures and enclosed environments.

One of the other big dangers with taking Molly is that some do it consider it a safer, purer form of ecstasy, which might not be true -- especially if it's been mixed with other substances, unknown to the user.

The effects of using Molly or ecstasy can last for days. The most common include anxiety and depression. But Rutter said there are more insidious effects that people should know about.

"One of the big problems is disrupted sleep," she said. "The long-term effect that this has on the brain can make it even harder to recover from the MDMA's effects. It might even prompt the cycle of drug addiction and cravings."